1. Field of the Invention
The invention relates to a device for segmenting textured images on the basis of digital signals which are representative of said images, by defining each texture by representative parameters and decomposition of each image into regions associated with the different textures. The invention can be used, for example for preprocessing images before their transmission and/or storage. The invention also relates to an image segmentation system comprising such a device.
2. Description of the Related Art
The transmission or storage of images within very short periods of time necessitates very high data rates which cannot generally be realised for economic and technical reasons. It is thus necessary to compress the information to be transmitted (or to be stored). Present data compression techniques are conventionally based on signal processing by means of an orthogonal transform with compression rates of about 10. Another approach, based on a better analysis of the images concerned and leading to higher compression rates, employs a method of preprocessing said images. Such method consists of considering the images as being constituted by an assembly of homogeneous regions each defined by a contour and an internal texture.
Such an image preprocessing method is described, for example, in the document "Segmentation adaptative pour le codage d'images", PhD thesis no. 691 (1987) presented by Mr. R. Leonardi at the Depanement d'Electricite de l'Ecole Polytechnique Felerale of Lausanne. It provides a correct segmentation into homogeneous regions when the luminance varies only weakly in each of these regions, but leads to a severe oversegmentation when these regions correspond to grass, raffia, wood textures etc. or, in general, to zones in which a sort of structured and more or less periodical aspect can be observed which is defined by a primary grain and one or several rules of disposition or repetition of this grain on an entire surface. For treating such textures, French Patent Application no. 2660459, whose introductory paragraph describes the diversity of currently known segmentation processes in accordance with the texture type concerned, proposes a segmentation method which is suitable for any type of image and comprises particularly the following basic steps: characterization of each texture by an assembly of parameters forming a prototype vector and classification by decomposition of the image into regions associated with the different textures, with a possible merging of the regions obtained.